Settlement induced by TBM excavation under the Vittoria's Church in Napoli

Line 6 of the Metro of Napoli underpasses one of the corner of an old church, built in the 16th century, with a tunnel of 8.5 m of external diameter at a depth of approximately 10 metres beneath its foundations. The tunnel has been excavated by means of a tunnel boring machine (TBM). During the design phase the presence of the church was carefully taken into account, with settlement predictions based on cautious range of volume loss during the construction of the tunnel. For its relevance the church was submitted to an accurate monitoring. The paper describes the monitoring system and presents the obtained results, which are also compared with the settlements measured in the greenfield sections located in the square and in the public gardens in front of the church. The influence of the stiffness of the structure and of the relative position of the underground line with respect of the plan section of the church is discussed in the last part of the paper